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Diffstat (limited to 'src')
-rw-r--r-- | src/compiler/scala/tools/nsc/matching/Patterns.scala | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/src/compiler/scala/tools/nsc/matching/Patterns.scala b/src/compiler/scala/tools/nsc/matching/Patterns.scala index b1bcf44c38..14e940d8a9 100644 --- a/src/compiler/scala/tools/nsc/matching/Patterns.scala +++ b/src/compiler/scala/tools/nsc/matching/Patterns.scala @@ -314,13 +314,20 @@ trait Patterns extends ast.TreeDSL { object UnapplyPattern { private object UnapplySeq { + /** This is as far as I can tell an elaborate attempt to spot case List(...) and + * avoid the extractor penalty. It has led to some bugs (e.g. 2800, 3050) which + * I attempt to address below. + */ private object TypeApp { def unapply(x: Any) = condOpt(x) { case TypeApply(sel @ Select(stor, nme.unapplySeq), List(tpe)) if stor.symbol eq ListModule => tpe } } def unapply(x: UnApply) = condOpt(x) { - case UnApply(Apply(TypeApp(tptArg), _), List(ArrayValue(_, xs))) => (tptArg, xs) + case UnApply(Apply(TypeApp(tptArg), _), List(ArrayValue(_, xs))) + // make sure it's not empty or only _*, as otherwise the rewrite + // also removes the instance check. + if xs takeWhile (x => !isStar(x)) nonEmpty => (tptArg, xs) } } |